Unusual magnetic changes in the Sun – The north pole of the Sun had started flipping about a year earlier than expected

While scientists had predicted that the next flip would begin from May 2013, the solar observation satellite Hinode found that the north pole of the sun had started flipping about a year earlier than expected. There was no noticeable change in the south pole.

The researchers found signs of unusual magnetic changes in the sun. Normally, the sun’s magnetic field flips about once every 11 years. In 2001, the sun’s magnetic north pole, which was in the northern hemisphere, flipped to the south. If that trend continues, magnetic field polarity at the solar poles will reverse and become quadrupolar in May, meaning positive fields will emerge in the North and South poles and negative fields will emerge on the equator, according to the National Astronomical Observatory of Japan and other institutes. A research team led by Saku Tsuneta, a professor at the observatory, analyzed solar magnetic fields data using Hinode, an observational satellite, and confirmed that the polarity of the magnetic field at the North Pole began to reverse in July last year.

Changes in Sun's magnetic poles (Credit: The Asahi Shimbun)

The research team believes the quadrupolar pattern also emerged in the 17th to 18th century. The Japanese study found that the trend of current sunspot activity is similar to records from Maunder Minimum, period about 300 years ago when temperatures are estimated to have been about 2.5 degrees lower than in the second half of the 20th century. Officials of the National Astronomical Observatory of Japan and the Riken research foundation said on April 19 that the activity of sunspots appeared to resemble a 70-year period in the 17th century in which London’s Thames froze over and cherry blossoms bloomed later than usual in Kyoto.

In 2008 in the Northern Hemisphereof the Sun (left) Hinude observed large patches of negative polarity, shown in orange. In 2011, the same area showed much smaller patches and a more even distribution of negative and positive (blue) regions. (Credit: JAXA/Hinode)

The Sun’s Poles

Like Earth, the Sun has a North Pole, a South Pole, and an equator. The poles of the Sun are different in several ways from the areas near the Sun’s equator. About every 11 years, the Sun’s magnetic poles flip – North becomes South and vice versa. This flip happens around the peak of the sunspot cycle, when there are lots of sunspots. Earth’s magnetic poles sometimes flip, too. However, it is usually many thousands or even millions of years between flips of Earth’s field - not just 11 years! The last polar reversal occurred around 750,000 years ago, but it can happen at shorter intervals, depending on prevailing circumstances. Some researchers think our planet is overdue for another one, but nobody knows exactly when the next reversal might occur. Many scientists, including Einstein, have predicted that another polar shift is close at hand. Several ancient civilisations have left records predicting global devastation and change. The Hopi Indian and Mayan calendars have predicted global devastation and an era of change starting in the year 2012.

The ongoing changes are not confined to the space immediately around our star, Hathaway added. The Sun’s magnetic field envelops the entire solar system in a bubble that scientists call the “heliosphere.” The heliosphere extends 50 to 100 astronomical units (AU) beyond the orbit of Pluto. Inside it is the solar system – outside is interstellar space.

About every 11 years the magnetic field on the sun reverses completely – the north magnetic pole switches to south, and vice versa. This flip coincides with the greatest solar activity seen on the sun in any given cycle, known as "solar maximum."

While the cycle unfolds with seeming regularity every 11 years, in two upcoming papers scientists highlight just how asymmetrical this process actually is. Currently the polarity at the north of the sun appears to have decreased close to zero – that is, it seems to be well into its polar flip from magnetic north to south -- but the polarity at the south is only just beginning to decrease.

"Right now, there's an imbalance between the north and the south poles," says Jonathan Cirtain, a space scientist at NASA's Marshall Space Flight Center in Huntsville, Ala., who is also NASA's project scientist for a Japanese solar mission called Hinode. "The north is already in transition, well ahead of the south pole, and we don't understand why."

One of the two papers relies on Hinode data that shows direct observations of this polar switch. The other paper makes use of a new technique observing microwave radiation from the sun's polar atmosphere to infer the magnetic activity on the surface.

The asymmetry described in the papers belies models of the sun that assume that the sun's north and south polarities switch at the same time. In addition, both papers agree that the switch is imminent at the north pole, well in advance of general predictions that solar maximum for this cycle will occur in 2013. Lastly, the direct Hinode results also suggest a need to re-examine certain other solar models as well.

Measuring the magnetic activity near the poles isn't easy because all of our solar telescopes view the sun approximately at its equator, offering only an oblique view of the poles, when they require a top-down view for accurate magnetic measurements. Hinode can observe this activity annually with its high resolution Solar Optical Telescope that can map magnetic fields when observing them from near the equator.

The microwave radiation technique described in the second paper makes use of the discovery in 2003 that as the sun moves toward solar maximum, giant eruptions on the sun, called prominence eruptions – which during solar minimum, are concentrated at lower solar latitudes -- begin to travel toward higher latitudes near the poles. In addition, the polar brightness in the microwave wavelengths declines to very low values.

"These prominence eruptions are associated with increased solar activity such as coronal mass ejections or CMEs, so CMEs originating from higher latitudes also point to an oncoming solar maximum," says Nat Gopalswamy. Gopalswamy is a solar scientist at NASA's Goddard Space Flight Center, who is the first author on the microwave observations paper, which was accepted by The Astrophysical Journal on April 11, 2012. "When we start to see prominence eruptions above 60 degrees latitude on the sun, then we know that we are reaching solar maximum."